Ab initio and semi-empirical Molecular Dynamics simulations of chemical reactions in isolated molecules and in clusters

Abstract

Recent progress in ''on-the-fly'' trajectory simulations of molecular reactions, using different electronic structure methods is discussed, with analysis of the insights that such calculations can provide and of the strengths and limitations of the algorithms available. New developments in the use of both ab initio and semi-empirical electronic structure algorithms are described. The emphasis is on: (i) calculations of electronic properties along the reactive trajectories and the unique insights this can contribute to the processes; (ii) electronic structure methods recently introduced to this topic to improve accuracy, extend applicability or enhance computational efficiency. The methods are presented with examples,including new results, of reactions of both isolated molecules and of molecules in media, mostly clusters. Possible future directions for this fast growing field are suggested.

Three pillars for achieving quantum mechanical molecular dynamics simulations of huge systems: Divide‐and‐conquer, density‐functional tight‐binding, and massively parallel computation

“…Fully QM simulations of large systems have also been performed using semi-empirical molecular orbital (MO) methods. [10] Recently, the density-functional tight-binding (DFTB) theory [11,12] has attracted considerable attention as an alternative because it is more accurate than other semiempirical MO methods with comparable computational demands. In particular, DFTB-MD simulations have been per-formed to elucidate the formation and/or transformation mechanisms of nanoscale carbon materials.…”

“…Fully QM simulations of large systems have also been performed using semi‐empirical molecular orbital (MO) methods . Recently, the density‐functional tight‐binding (DFTB) theory has attracted considerable attention as an alternative because it is more accurate than other semi‐empirical MO methods with comparable computational demands.…”

Parallel implementation of efficient charge–charge interaction evaluation scheme in periodic divide‐and‐conquer density‐functional tight‐binding calculations

“…Quantum mechanical molecular dynamics (QM‐MD) simulations are being increasingly applied for obtaining atomistic insights into chemical reactions and/or dynamical processes of materials and biomolecular systems . One of the challenges in QM‐MD simulations is the limited system size on account of high computational demands for solving the electronic structure problem with formal scaling of a cubic or higher with respect to system size.…”

“…Quantum mechanical molecular dynamics (QM-MD) simulations are being increasingly applied for obtaining atomistic insights into chemical reactions and/or dynamical processes of materials and biomolecular systems. [1][2][3] One of the challenges in QM-MD simulations is the limited system size on account of high computational demands for solving the electronic structure problem with formal scaling of a cubic or higher with respect to system size. Several approaches have been developed to describe large systems under a full QM treatment, such as semi-empirical methods, [4,5] parallel computing of realspace density functional theory (DFT), [6][7][8] direct optimization of density matrix or expansion coefficients with an iterative procedure, [9,10] and fragmentation-based methods.…”

Interatomic Coulombic decay widths of helium trimer: A diatomics-in-molecules approach

“…Furthermore, it requires only accurate energies of atoms and diatomic molecules which can nowadays be obtained with advanced and reliable quantum chemistry methods. DIM methods have been succesfully employed for describing small molecules [34,35] as well as pure and doped raregas clusters [36][37][38][39]. Here, in the spirit of the DIM, we propose to compute the ICD widths of rare-gas clusters from the widths of each pair of atoms forming the cluster.…”